In preliminary studies we have demonstrated a potent inhibition of erythrocyte membrane Ca-stimulated-ATPase (Ca-ATPase) by zinc. Zinc inhibition of Ca-ATPase at concentrations down to 10 microns M has been shown by both inhibition in a Ca-ATPase (Pi) assay system and by inhibition of phosphorylation at the site of the Ca-ATPase protein bands in SDS-PAGE. In further but very preliminary work we have demonstrated zinc inhibition of Ca-ATPase activity from platelets. This work on a possible molecular effect of zinc on membranes is a follow-up to our earlier demonstration of an antisickling effect of zinc both in vitro and in vivo. In the laboratory, zinc at low concentrations improves sickle red cell filterability. In patients with sickle cell anemia, oral zinc therapy has reduced the count of irreversible sickled cells (ISCs) in the circulating blood. ISCs are membrane-damaged cells. These effects occur at such low concentrations of zinc that we have postulated a membrane effect of zinc as opposed to a hemoglobin effect. In other preliminary studies, zinc has been shown to have an ATP-preserving effect during prolonged incubations of red cells. This observation led to study of zinc effects on Ca-ATPase because this enzyme is capable of rapid hydrolysis of ATP in the presence of increased calcium levels. In the proposed work, we plan to investigate the effects of zinc on the Ca-ATPase activity of not only isolated membrane preparations, but whole hemolysates, and intact normal red cells. A recently described activator of Ca-ATPase (Colmodulin) will feature prominently in these studies, in terms of interaction with zinc inhibition. The role of hemoglobin, which binds zinc, will be studied. The work in intact cells is very important, because it will test whether or not zinc inhibition of Ca-ATPase is relevant when the whole system is put back together. The work will be extended to sickle red cells, since preliminary evidence indicates some differences in sensitivity to zinc compared to normal cells. Ca-ATPase inhibition by zinc in sickle cells will be evaluated in both assay and SDS-PAGE systems, as will normal red cells. Finally, the same sequence will be carried out with platelet Ca-ATPase. The ultimate objectives are to fully characterize zinc inhibition of Ca-ATPase (and other ATPases), and to tr (Text Truncated - Exceeds Capacity)